1. Field of the Invention
This invention relates to a blood filter and method of using thereof for trapping and removing emboli during an endovascular procedure.
2. Description of the Prior Art
Advances in medicine and technology are leading to development of minimally invasive surgical techniques for treatment of various medical conditions. For example, stenosis formed in a blood vessel may be treated endovascularly using techniques such as balloon angioplasty, stent placement, or thrombolysis. However, the use of such endovascular techniques has been limited due to embolization of debris from the treated portion of the vessel to a downstream portion resulting in complications. For example, treatment of a stenosis in a carotid artery can result in ischemic complications and possible embolic stroke. Thus, there is a need for a device to trap emboli which may result from endovascular treatment of a blood vessel.
Many blood filters are in the prior art which are formed to trap emboli. A number of permanently implantable blood filters were developed in the prior art for capturing clots developed post-operatively in a patient subjected to extensive periods of bed rest. These filters are intended to be implanted in the inferior vena cava to prevent the passage of clots into the lungs. For example, U.S. Pat. No. 3,540,431 to Mobin-Uddin, entitled "COLLAPSIBLE FILTER FOR FLUID FLOWING IN CLOSED PASSAGEWAY", discloses an umbrella-shaped filter which is spring biased to have an open configuration in its natural state. Upon release from an introducer catheter into the inferior vena cava, the Mobin-Uddin filter springs into an open configuration with the spokes of the filter being in pressing engagement with the vessel wall. A second example of a permanently implantable blood filter is disclosed in U.S. Pat. No. 3,952,747 to Kimmell, Jr., entitled "FILTER AND FILTER INSERTION INSTRUMENT", also known as the Greenfield-Kimray filter. The Greenfield-Kimray filter comprises a plurality of spring biased bent wires extending from a single central hub. Upon ejection from an introducer instrument into a blood vessel, the Greenfield-Kimray filter expands to engage the wall of the vessel. Generally, the permanently implantable blood filters are configured to trap life-threatening emboli, considered to be 3 mm or larger in diameter. The trapped emboli are broken down by blood passing through the respective filter, with the emboli eventually being eroded to a harmless size. It can be appreciated, other than through surgical removal, no practical method is disclosed for removing permanently implantable blood filters. Thus, this type of blood filter would have to be left in a blood vessel if used during an endovascular procedure, which may be undesirable.
Retrievable blood filters are also known in the prior art which can be removed through the blood vessel without requiring surgery. Some examples are U.S. Pat. No. 4,619,246 to Molgaard-Nielsen et al., entitled "COLLAPSIBLE FILTER BASKET", and U.S. Pat. No. 5,329,942 to Gunther et al., entitled "METHOD FOR FILTERING BLOOD IN A BLOOD VESSEL OF A PATIENT".
U.S. Pat. No. 4,873,978 to Ginsburg, entitled "DEVICE AND METHOD FOR EMBOLI RETRIEVAL", discloses a retrievable blood filter for trapping and removing emboli from a blood vessel, during and after an endovascular procedure. Ginsburg discloses a collapsible filter which is introduced, via a catheter in an upstream direction in a blood vessel to a location downstream from a stenosis which is to be treated. A stenosis treatment device is introduced, via a second catheter, in a downstream direction to the stenosis. Any emboli dislodged during the treatment of the stenosis travel downstream in the blood vessel and are trapped in the Ginsburg filter. The Ginsburg filter is collapsed and removed after treatment is completed with any trapped emboli being removed therewith. It is readily apparent, however, that the required insertion of two separate catheters into a patient to complete treatment and blood filtering is a drawback of the Ginsburg filter.
It is an object of the subject invention to provide a collapsible filter for trapping emboli during and after an endovascular procedure.
It is also an object of the subject invention to provide a method for filtering blood during an endovascular procedure for the trapping and removal of emboli therefrom.